Some of the images in your first gallery do not display because the imageURLs in the gallery's XML file do not match the actual image filenames.For example, the first image that does not display is listed as 'DSC01809.jpg' in the XML file but the image itself is named 'DSC01809.JPG'. Your web server is case-sensitive and .jpg is not the same as .JPG.

Also, having alignment problems as you might can see. On some browsers, it is lined up right, on others it's to the left.

Your 'gallery.html' page does not have a Doctype Declaration at the top.Without knowing what set of standard to conform to, browsers may render your page unpredictably.Looking at your code, the most appropriate Doctype would be HTML 4.01 Transitional, in which case place the following code at the very top of your web page before the opening <html> tag:

Also, as your gallery is in a <table>, it might be wise to set the required dimensions in the <td> tag and then set your gallery's own dimensions to 100% x 100% so that the gallery fills the container from edge to edge (and is therefore centered). Setting the gallery's dimensions to 75% x 75% (as they are at present) means that it will fill only the upper left portion of the <td>. The will give the impressions that the gallery is offset to the left.